1. Field of the Invention
This invention generally relates optical recording and, more particularly, to a near-field optical probe and an optical near-field generator that generates an optical near-field.
2. Discussion of Background
In recent years, a probe that uses a planar metal scatterer has been proposed for optical recording. This is a probe in which a planar metal scatterer 351 in the shape of a triangle is formed on a flat substrate, as shown in FIGS. 43A and 43B. FIG. 43A shows a probe in which a single metal scatterer 351 is formed, and FIG. 43B shows a probe in which two metal scatterers 351 are formed. When light polarized in an X-direction is made to enter the probe, an optical near-field localized at a vertex 352 is generated. Particularly, by matching the wavelength of the incident light with resonance of plasmons, an extremely intense optical near-field can be generated (see Technical Digest of 6th International Conference on Near Field Optics and Related Techniques, the Netherlands, Aug. 27-31, 2000, p.55).
In the case of FIG. 43A, the optical near-field is generated from the vertex 352 of the metal scatterer 351, while in the case of FIG. 43B the two metal scatterers 354 are arranged so that a spacing between vertices thereof is a few tens of manometers to generate the optical near-field localized between the vertices 353. Note that in this description an optical near-field means localized light, namely light whose wave number has an imaginary component.
[Non-Patent Reference 1]
Technical Digest of 6th International Conference on Near Field Optics and Related Techniques, the Netherlands, Aug. 27-31, 2000, p.55.
The probe that uses the above-mentioned planar scatterer in the shape of a triangle is capable of realizing an extremely high optical near-field generation efficiency. With this probe, if the frequency of light and the resonance frequency of the plasmons generated in the metal are matched, an extremely high efficiency can be obtained.
However, when using a planar scatterer as described above, weak optical near-fields are generated at parts of the scatterer (hereinafter referred to as “the parts”) except for the vertex at which the optical near-field is generated. For example, in the case where a scatterer in the shape of a triangle as shown in FIGS. 1A and 1B is used, in order to generate plasmon resonance, it is preferable that the length of the scatterer (L1) is set not larger than light wavelength. At this time, vertices 13 other than the vertex 12 at which an intense optical near-field is generated also exist within a light spot for excitation. Unfortunately, weak optical near-fields are also generated at these vertices 13. If the optical near-fields are generated also at the vertices 13 in this way, when observing a sample or reproducing recording marks, scattered light that is generated therefrom is detected as noise.